# Magnitude of Perpendicular Component.

## Homework Statement

Determine the components of F that act along rod AC and perpendicular to it. Point B is locateda distance f along the rod from end C

http://imgur.com/iGJkN
Given:
F = 600 N
a = 4 m
b = 6 m
c = 4 m
d = 3 m
e = 4 m
f = 3 m

## The Attempt at a Solution

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Ibix
If you knew that - for the sake of argument - the rod lay along the vector (1,2,3) and the force was acting along (8,-1,6), could you solve the problem?

how did you get those numbers.

Ibix
I pulled them out of the air. I'm trying to find out what you know how to do.

I'll infer from your answer that your problem is that you don't know how to get the directions of the rod and the force, but could take it from there.

You need the vectors along the rod and the force. You can always get these by writing the position vectors of two points in the line of the rod/force and taking the difference.

The point A is on the rod. It lies a distance a directly above the origin, so its position vector is (0,0,a). Can you find another point on the rod, and two on the line of the force?

if i take the magnitude of the rod AC then subtract 3 m will i be able to get point B. then i would be able to find the vector components of force BD.

i found a solution her but it does not show all the steps and i cant understand it.
http://www.scribd.com/doc/48470460/113/Problem-2-116 [Broken]

Last edited by a moderator:
SammyS
Staff Emeritus
Homework Helper
Gold Member

## Homework Statement

Determine the components of F that act along rod AC and perpendicular to it. Point B is located a distance f along the rod from end C

http://imgur.com/iGJkN
Given:
F = 600 N
a = 4 m
b = 6 m
c = 4 m
d = 3 m
e = 4 m
f = 3 m

## The Attempt at a Solution

A start would be to find a unit vector directed along the line from point A to point C, and a unit vector directed along the line from point B to point D, the latter one being in the direction of the force vector, F.

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i have found the direction vector of AC, but i dont know how they got the "r" value.

i have gotten to the step where finding the parallel component of the vector. am i supposed to use dot product to find projection.

SammyS
Staff Emeritus
Homework Helper
Gold Member
i have found the direction vector of AC, but i don't know how they got the "r" value.
i have gotten to the step where finding the parallel component of the vector. am i supposed to use dot product to find projection.